Single or multiple lumen catheters are well known in the medical field and are widely used in medical procedures such as hemodialysis or other procedures wherein it is desirable to inject or remove fluids through one or more lumens of the catheter. For example, in hemodialysis it is desirable to introduce blood into a vein or other vessel of a patient through a first lumen while simultaneously removing a corresponding amount of blood from the patient through a second lumen of the catheter. In certain situations, it may also be desirable to have a third lumen extending through the catheter to allow a medication to be injected therethrough without interfering with the operation of the first or second lumens.
The currently available single or multiple lumen catheters frequently have an opening at the distal end thereof and one or more openings or holes along the sidewall of the catheter. During hemodialysis, the arterial or intake lumen is used to remove blood from the patient. This intake lumen typically opens along the sidewall of the catheter. In use, the side opening may occasionally become completely or partially occluded by the interior wall of the patient's blood vessel when the catheter has been inserted. The complete or partial occlusion of the side opening will significantly reduce the flow of blood through the intake lumen of the catheter and may also damage the interior wall of the patient's blood vessel.
In certain commercially available catheters one or more relatively large side openings are used. With these side openings it is typically recommended that the flow of fluid through the side opening be checked prior to hemodialysis. If the side opening is occluded, it is recommended that the catheter be rotated or otherwise repositioned. A further difficulty with the use of the large single side opening is that the side opening may occasionally get caught on the tissue or the wall of the blood vessel along the incision during insertion. Yet another difficulty with the use of a large single side opening is that the catheter may kink or bend at the side opening during insertion if the catheter tip meets resistance during insertion because the large side opening may weaken the column strength of the catheter.
In other commercially available catheters, as disclosed in U.S. Pat. No. 4,543,087 granted to Sommercorn et al., a plurality of spaced apart side openings are provided so that even if one side opening is occluded at least one of the remaining side openings may remain open. Another approach to solving the problem of occlusion is disclosed in U.S. Pat. No. 4,795,439 granted to Guest. In this patent, the lumens of the distal portion of the catheter are twisted such that the plurality of side openings in the catheter are not aligned in a straight line along the distal portion of the catheter. A further catheter design is shown in U.S. Pat. No. 4,808,155 granted to Mahurkar wherein a blunt distal end is provided on the catheter and the shorter intake lumen includes a bevel thereon which ends proximally of the return lumen.
The use of multiple side openings in a catheter provides an increased likelihood that a clot may form along or in one or more of the side openings as compared to the likelihood of clotting in catheters with a single side opening for each lumen. This increased likelihood of clot formation is believed to be caused, at least partially, by the presence of multiple surfaces between each of the side openings which may provide an area of reduced flow in the lumen which allows the clot to form thereon. Additionally, it is a common practice to perform a heparin flush of the catheter periodically to decrease the likelihood of clot formation on the catheter. The heparin flush technique is believed to be less effective in removing or preventing clot formation in catheters with multiple side openings because if one of the side openings is occluded by a clot, the heparin will merely flow through the side opening which provides the least resistance. There is also the possibility that the heparin may be washed out of the distal portion of the lumen of the catheter by blood which may enter one or more of the proximally located side openings to flush the heparin through the lumen and out of the catheter through one or more of the distally located side openings.
One final approach to solving the problem of preventing occlusion and clot formation involves the use of elongate slits as side openings in the catheter. The slits completely close the lumen between uses and are opened only upon the application of either positive or negative pressure to the fluid in the lumen of the catheter. One difficulty with this approach is that it requires increased pressure through the lumens of the catheter to open the slit openings during use. Additionally, if the blood is not completely removed from the lumen by the heparin flush, the stagnant flow of fluid in the lumen may result in the formation of a clot in the lumen which will be difficult to remove through the slit.
The present invention overcomes the disadvantages described above by providing an elongated side opening which is preferably oriented diagonally along the distal portion of the catheter to retain the column strength of the catheter while minimizing the likelihood of occlusion or clot formation.